The present invention relates to a solder ball connection device for connecting a bonding pad formed at a slider provided with a head, and a lead pad formed at the tip of a lead wire. More particularly, the present invention relates to a tube employed for the solder ball connection apparatus and used to position and hold a solder ball in a solder reflowing process.
FIG. 8 shows a perspective view of the HG assembly suitable for electrical connection between a lead wire and a slider with use of a solder ball connection method. FIG. 9 is an expanded view of the tip of the HG assembly. The external shape of the HG assembly 100 is defined by an actuator arm 101 provided with an opening 102 and a load beam 104 extended in the longitudinal direction of the actuator arm 101 from an intermediate portion of its flat portion 103. The actuator arm 101 and the load beam 104 are bonded together at a portion where they are placed on top of each other.
The opening 102 is used so that the HG assembly 100 is held rotationally by a holder of a magnetic disk apparatus (not shown). The HG assembly 100, passing through the center of the opening, is rotated in the directions A and B around a virtual axis 150 substantially perpendicular to the flat portion 103. A mount plate 105 is bonded to the load beam 104 substantially in the center portion so as to be put thereon. A flexure 106 is also disposed on the load beam 104 between the center and the tip thereof. This flexure 106 is bonded to the load beam 104 by a half located at the side of the mount plate 105. The other half of the flexure 106 located at the side of the tip is not bonded to the load beam 104.
As shown in FIG. 9, at the tip of the flexure 106 is formed an arch-shaped opening 107 and the slider 109 is bonded fixedly to a flexure tang 106a (FIG. 10) formed so as to be protruded to the center of the arch-shaped opening 107 from a platform 108 formed at the extreme tip of the flexure 106. This flexure tang 106a is supported by a pivot 104a (shown with a broken line in FIG. 10) protruded from the load beam 104 at one point corresponding to the center of the slider 109. Consequently, the slider 109 can be inclined at a predetermined angle (often referred to as a pitch, a roll, or a yaw) in every direction with respect to the load beam 104.
Four leads 110 to 113 are wired partially to an extended portion 105a of the mount plate 105. They are fixed at the extended portion 105a with an insulating sheet therebetween respectively so as not to touch each other. At one ends, they compose a multi-connector 114. The four leads 110 to 113 are connected to the mount plate 105 and the flexure 106 respectively as shown in FIG. 8 and fixed so as not to touch each another with an insulating sheet therebetween respectively. The other ends of the leads are floated in the arch-shaped opening 107 as shown in FIG. 9 and they are paired, crank-bent, and led to the platform 108.
The paired leads are bent substantially perpendicular to the front surface 109a of the slider 109 through two openings 114 and 115 formed between the platform 108 and the flexure tang 106a (FIG. 10). In addition, the lead pads 110a to 113a are formed corresponding to the connection surfaces of the four bonding pads 116 to 119 formed at this front surface 109a. The four leads 110 to 113 are fixed to the platform 108 around their tips with an insulating sheet 20 therebetween respectively. A part of the HG assembly, where the slider 109 does not exist, is equivalent to the slider holder.
The following is a description of a solder ball connection method for connecting the four bonding pads 116 to 119 to the lead pads 110a to 113a formed so as to be corresponded to those bonding pads 116 to 119.
FIG. 10 is a sectional view of the major portion of the HG assembly from the direction C at a directing line 151. The directing line 151 passes the center of the bonding pad 118 shown in FIG. 9. FIG. 10 also shows a partial cross sectional view of the solder ball connection device. The load beam 104 is not illustrated here so as to simplify the description, but the position of the pivot 104a formed at the load beam 104 is shown with a broken line.
When carrying out a solder ball connection, the inclined HG assembly 100 (FIG. 8) is held by a holder (not shown) so that the pad connection surface 118a of the bonding pad 118 and the connection surface 112b of the lead pad 112a face each other substantially perpendicular and each of those connection surfaces 118a and 112b is inclined substantially at 45xc2x0 in the direction in which its gravity works.
On the other hand, the capillary tube 121 composes a part of the solder ball connection device (not shown). The capillary tube 121 is disposed in the direction in which the center axis 152 of the cylindrical inner hollow portion 121a can use the gravity, that is, at a position where the tip of the capillary tube 121 comes close to both of the bonding pad 118 and the lead pad 112a while being inclined at about 45xc2x0 to the connection surface 112b of the lead pad 112a. 
The solder ball connection device (not shown) stores many solder balls 122 and sends one solder ball 122 to the tip of the capillary tube 121 through its inner hollow portion 121a after the capillary tube 121 is disposed at a predetermined position. At this time, the apparatus supplies a nitrogen gas (N2) in the direction of the arrow a so as to prompt the solder ball 122 to move together with the action of the gravity. In addition, the nitrogen gas also presses the solder ball 122 slightly that is in contact with both connection surfaces 118a and 112b of the bonding pad 118 and the lead pad 112a when the solder ball 122 exists at the tip of the capillary tube 121.
In this state, the solder ball connection device (not shown) applies a laser beam (shown with a broken line LZ in FIG. 10) to the solder ball 122 through the inner hollow portion 121a of the capillary tube 121 so as to make the solder ball reflow. The solder ball 122 is then melted in this reflowing, getting both connection surfaces 118a and 112b of the bonding pad 118 and the lead pad 112a wet and connected together. The nitrogen gas supplied at this time presses the melted solder against each connection surface and cover the solder so as to be prevented from oxidation.
This completes the description of the solder ball connection for the bonding pad 118 of the slider 109 and the lead pad 112a of the lead 112. The same procedure can also apply to the connections of other three pads only by changing each position to which the capillary tube 121 is provided.
FIG. 11 is a perspective view of the tip shape of the capillary tube 121. The conic tip of the capillary tube is cut as shown in FIG. 11 so that its cross section perpendicular to the center axis 152 is formed like a ring. In this case, as shown in FIG. 10, it is difficult to move the tip of the capillary tube 121 down up to the regulation point P1 orthogonal to the center line 152 through the center of the solder ball 122, which is in contact with both pads. This is because the tip of the capillary tube 121 comes in contact with any of the pads before reaching the regulation point P1, thereby its up and down movement is disturbed by the pad.
If the tip of the capillary tube 121 does not reach the regulation point P1 as described above, the solder ball 122 can take an idle width at which the solder ball 122 can move in the direction parallel to both connection surfaces 118a and 112b of the bonding pad 118 and the lead pad 112, that is, in the direction passing through the paper with FIG. 10. Consequently, the solder ball 122 comes to reflow the solder ball in an unstable state, thereby the soldering position cannot be decided accurately or a connection failure occurs due to uneven irradiation of the laser beam on the solder ball. Furthermore, as shown in FIG. 10, the laser beam, which passes the inner hollow portion 121a of the capillary tube 121 so as to reflow the solder ball, hits and reflects here and there on the inner wall of the hollow portion 121a until it reaches the solder ball. The energy of the laser beam is thus attenuated due to such reflections, thereby the irradiation efficiency of the laser beam is lowered. To compensate such an attenuation, therefore, the output of the laser beam has been increased as much.
Under such a circumstances, it is an object of the present invention to provide a method for positioning a solder ball to reflow accurately and stabilize the soldering point so as to make the connection perfect, thereby preventing connection failures. It is another object of the present invention to provide a method for making solder ball connection more efficient by reducing the energy loss caused by reflections of the laser beam, thereby reducing the energy loss of the laser beam when in solder reflowing.
A capillary tube is employed for a solder ball connection device for connecting a first connection surface of a pad to a second connection surface of a pad with use of a solder ball. The pad has the first connection surface formed at a slider held by a slider holder in a disk unit. The pad has the second connection surface formed at an end of a lead wired to the slider holder. The capillary tube has a ball regulator provided with a substantially conic and hollow portion inside. The solder ball regulator has an opening at its top. The opening opens to the tip of the hollow portion. The center axis of the hollow portion is common to the center axis of the opening. The solder ball regulator also has a pair of projections protruded along the center axis at a position around the opening, where those projections face each other with the center axis therebetween. These projections regulate the movement of the solder ball.
The tip of the hollow portion is tapered when viewing it from the direction of a line connecting the pair of projections and the extreme tips of the tapered tip portions to each other may be used as the projections. The tip may also be formed by a pair of flat surfaces inclined to a datum level including a line connecting the center axis and the pair of projections to each other. The pair of flat surfaces may have the same angle respectively to the datum level and the pair of projections may be symmetrical to the datum level.
In another configuration, the capillary tube is connected to the other side end of the tip portion of the solder ball regulator and formed on the same axis as that of the solder ball regulator. The capillary tube has a cylindrical portion provided with a hollow portion continued to the hollow portion of the solder ball regulator from the viewpoint of space. Furthermore, the inside surfaces of the pair of projections may be a part of a cylindrical surface formed on the same axis as that of the hollow portion respectively.
In still another configuration, the inside surface of the solder ball regulator is polished like a mirror.
In still another configuration, the solder ball regulator and the cylindrical portion, or at least the solder ball regulator, are composed of a first tube-like body and at least a part of the cylindrical tube is composed of a second tube-like body. And, the capillary tube is further provided with a connector for connecting the first and second tube-like bodies to each other.
In still another configuration, the tip portion of the capillary tube is formed with a pair of first flat portions and a pair of second flat surfaces. The pair of the first flat surfaces are inclined by a first angle to the datum level including a line connecting the center axis and the pair of projections and the pair of the second flat surfaces are continued to the pair of the first flat surfaces and inclined by a second angle to the datum level.
The solder ball connection device, which is another invention, is provided with a capillary tube described in claim 1; a solder ball reservoir for supplying a solder ball into the capillary tube, the diameter of the solder ball being smaller than the inner diameter of the opening; and a laser output device for applying a focused laser beam to the opening of the capillary tube through the hollow portion. The datum level including a line connecting the center axis, as well as the first and second projections of the capillary tube is set so as to be inclined to the first and second connection surfaces, thereby the solder ball is reflowed.
In another configuration, the solder ball connection device is provided with a capillary tube described in claim 4; a solder ball reservoir for supplying a solder ball into the capillary tube, the diameter of the solder ball being smaller than the inner diameter of the opening; and a laser output device for applying a focused laser beam to the opening of the capillary tube through the hollow portion. The datum level including a line connecting the center axis, as well as the first and second projections of the capillary tube is set so as to be inclined by 45xc2x0 to the first and second connection surfaces, thereby the solder ball is reflowed.
Furthermore, the solder ball connection device is further provided with a nitrogen gas supplier for supplying a nitrogen gas into the capillary tube.